A white-light emitting device (hereafter, LED) generally comprises of a blue-light LED combined with a yellow-light emitting Y3Al5O12:Ce3+ (hereafter, YAG:Ce) phosphor, that is excited by the blue light. Because of thermal effects resulting from the heat accumulation, the peak wavelength of the blue-light LED changes, and then the dominant wavelength and thereby the emission color of the white light shift. Moreover, the junction temperature of the blue LED rises as applied drive current increases, thus radiation power of the blue-light LED and conversion efficiency of the phosphor decrease.